08 Aug Excavations
Excavations are any man-made cut, cavity, hole, trench, or depression made in the earth’s surface by the removal of soil. Workers in excavations can be exposed to cave-ins, engulfment, hazardous atmospheres, and falls. Excavation safety training and procedures prevent serious injuries and accidents.
Before work on an excavation can begin, surface hazards such as unstable buildings, sidewalks, etc. that could endanger employees must be secured or removed. Hazards below the ground must also be identified and made safe before work can begin. Call 811 at least 2 days before the excavation. They will contact utilities so that representatives can determine if there are buried pipes or utilities in the planned work area. Excavations near sewers, landfills, chemical plants, and storage tanks for hazardous materials may have hazardous atmospheres. Excavations require inspection for hazardous atmospheres like low oxygen levels, high chemical concentrations, and/or flammable/explosive gases. Excavations deeper than 4 feet need to have atmospheric testing. If there are atmospheric hazards present or they could be present, ventilation, respiratory protection, and rescue equipment must be provided for worker safety.
Signs of soil distress near an excavation may indicate collapse or cave-in dangers. Fissures, cracks, or sagging/slumping materials from the open face of the excavation can indicate a hazard. Bulges at the excavation bottom, sinking at the edge, and small amounts of dirt and rock falling into the excavation are also signs of instability.
In California, if the excavation is more than 5 feet deep, it needs a permit from Cal/OSHA and there needs to be a protective system (benching, shoring, sloping, etc.) in place to protect the workers inside. For excavations more than 4 feet deep, there needs to be a way to enter and exit the work area at least every 25 feet via a ladder, ramp, or other sturdy device.
Excavation inspections are required before work starts, during work shifts, and after rainstorms. A competent person that is familiar with excavation regulations and safety systems, how to type soils, and how to recognize excavation hazards must do these inspections. Inspectors should look for signs of cave-ins, failing protective systems, and potentially hazardous atmospheres. If hazards are found, workers should exit the excavation until the work area is made safe.
To protect workers from falling soil and rocks during excavation operations, perform maintenance scaling of the open excavation face to remove loose rocks from the excavation face. Use protective shields and retaining fences to hold back loose material. Keep spoils, supplies, equipment, vehicles, and workers at least two feet from the working edge.
Avoid working in excavations that hold or accumulate water. If work MUST be done in this situation, use protective shield systems, pumping devices, and harnesses with safety lines as added protection. The pumping system must be monitored by a competent person. Diversion systems and dikes can be used to re-direct flowing and encroaching water sources.
Protection for excavations and trenching
- Access and Means of Egress – Stairs, ladders or ramps shall be provided where employees are required to enter trench excavations over 4 feet deep. The maximum distance of lateral travel (e.g., along the length of the trench) required to reach the means of egress shall not exceed 25 feet.
- Structural Ramps – Structural ramps used solely by employees as a means of access or egress from excavations shall be designed by a competent person. Structural ramps used for access or egress of equipment shall be designed by a person qualified in structural design, and shall be constructed in accordance with the design.
- Ramps and runways constructed of two or more structural members shall have the structural members connected together to prevent movement or displacement.
- Structural members used for ramps and runways shall be of uniform thickness.
- Cleats or other appropriate means used to connect runway structural members shall be attached to the bottom of the runway or shall be attached in a manner to prevent tripping.
- Structural ramps used in place of steps shall be provided with cleats or other surface treatments on the top surface to prevent slipping.
- Ladders – When portable ladders are used, the ladder side rails shall extend a minimum of 3 feet above the upper surface of the excavation.
- Ladders shall have nonconductive side rails if work will be performed near exposed energized equipment or systems.
- Two or more ladders, or a double-cleated ladder, will be provided where 25 or more employees will be conducting work in an excavation where ladders serve as the primary means of egress, or where ladders serve two-way traffic.
- Ladders will be inspected prior to use for signs of damage or defects. Damaged ladders will be removed from service and marked with “Do Not Use” until repaired.
- Ladders shall be used only on stable and level surfaces unless secured. Ladders placed in any location where they can be displaced by workplace activities or traffic shall be secured, or barricades shall be used to keep these activities away from the ladder.
- Non-self-supporting ladders shall be positioned so that the foot of the ladder is one-quarter of the working length away from the support.
- Employees shall not be allowed to carry any object or load while on the ladder that could cause them to lose their balance and fall.
- Exposure to Vehicular Traffic – Employees exposed to vehicular traffic shall be provided with, and shall wear vests or other suitable garments marked with or made of reflectorized or high-visibility material. Warning vests worn by flagmen shall be red or orange, and shall be of reflectorized material if worn during night work.
- Employee Exposure to Falling Loads – No employee shall be permitted underneath loads (or where loads may fall) handled by lifting or digging equipment. Employees shall be required to stand away from any vehicle being loaded or unloaded to avoid being struck by any spillage or falling materials. Operators may remain in the cabs of vehicles being loaded or unloaded when the vehicles provide adequate protection for the operator during loading and unloading operations.
- Warning System for Mobile Equipment – A warning system shall be used when mobile equipment is operated adjacent to the edge of an excavation if the operator does not have a clear and direct view of the edge of the excavation. The warning system shall consist of barricades, hand or mechanical signals, or stop logs. If possible, the grade should be away from the excavation.
- Hazardous Atmospheres – The atmosphere shall be tested for air contaminants (oxygen, flammable gases, etc.) in excavations over 4 feet deep or if a hazardous atmosphere exists or could reasonably be expected to exist. A hazardous atmosphere could be expected, for example, in excavations in landfill areas, in excavations in areas where hazardous substances are stored nearby, or in excavations near or containing gas pipelines.
- Adequate precautions shall be taken to prevent employee exposure to atmospheres containing less than 19.5 percent oxygen and other hazardous atmospheres. These precautions include providing proper respiratory protection or forced ventilation of the workspace.
- Forced ventilation will be provided where necessary to ensure the atmosphere is safe.
- When controls are used that are intended to reduce the level of atmospheric contaminants to acceptable levels, continuous air monitoring will be performed. The device used for atmospheric monitoring shall be equipped with an audible and visual alarm.
- Atmospheric testing will be performed using a properly calibrated direct reading gas monitor. Direct reading gas detector tubes or other acceptable means may also be used to test potentially toxic atmospheres.